1. Field of the Invention
This invention relates, generally, to aspiration biopsy needles. More particularly, it relates to an aspiration biopsy needle having an enhanced cellular material collection capability.
2. Description of the Prior Art
There are three main types of biopsy procedures. In a first type, a conventional surgical incision is made and the patient's body is opened so that a surgeon may retrieve one or more large pieces of the tumor or lesion to be tested for malignancy. This type of biopsy is very invasive, expensive to perform, and requires a considerable recovery time. Inventive endeavors in the field have resulted in two improved procedures that substantially reduce the invasiveness of the biopsy procedure, as well as the expense of the procedure and the length of the recovery time.
The first improved procedure involves the cutting or shearing of one or more visible pieces of the tumor or lesion by a relatively large bore needle. This type of biopsy is known an a core tissue biopsy and is performed with a core tissue biopsy needle. The pieces of tissue are usually about one to three millimeters in length and are thus visible to the unaided eye. They cannot be immediately examined under a microscope because they are too thick for light to pass therethrough. Accordingly, they must first be sliced into a plurality of very thin slices by a tissue-slicing machine. After slicing, they are then stained with a tissue fixative e.g., formalin, glutaraldehyde, etc., and placed upon a microscope slide for diagnostic purposes. For a period of time sufficient to cause crosslinking of connective tissue proteins present in the tissue, the fixed tissue is sliced into thin sections approximately eight (8) microns thick, the tissue sections are mounted on slides and cell-selective histiological stains are applied to stain the tissue prior to microscopic examination. This non-frozen tissue preparation technique typically requires twenty four to forty eight (24-48) hours to complete so the pathologist's diagnosis of the breast lesion may not be available until twenty four to seventy two (24-72) hours after the biopsy specimen was removed from the breast. Accordingly, histopathological examination and diagnosis of breast lesions may be much more time-consuming than the histopathological examination and diagnosis of other types of lesions.
The use of a core tissue biopsy needle thus represents a significant improvement over the more invasive surgical removal of tumor or lesion specimens. However, the need to slice the specimens causes a delay in providing the diagnosis, due to processing. Additionally, the diameter of core biopsy needles are typically larger than the diameter of fine needle aspiration (FNA) needles, thereby increasing the risk of procedure-related complications including bleeding, pneumothorax, and bile leakage. Moreover, the use of core biopsy needles necessitates the purchase and maintenance of tissue slicing machines. The material must be removed from the needle, deposited onto the machine, machine-sliced, removed from the machine after slicing, stained, and deposited onto a microscope slide.
One example of a core tissue biopsy needle is disclosed in U.S. Pat. No. 5,320,110 to Wang. The Wang structure has utility in performing a pleural tissue biopsy by cutting tissue samples of the parietal pleura. Wang teaches a two needle (tube-in-tube) system having a sharp edge to fix tissue while a second needle is advanced to shear off a piece of the tissue. The device does not rely solely on a vacuum to draw in material as in an FNA biopsy needle and tissue is sheared off in sizeable, visible pieces, i.e., not at the cellular level.
More particularly, in the Wang device, a hook engages the pleural tissue and an outer cannula is advanced to cut off the hooked piece of pleural tissue. This two needle system is designed to reduce the chances of a pneumothorax and thus represents a significant improvement over earlier biopsy techniques. However, the diameter of the Wang needle as described is about 4.5 mm, which is considerably larger than an FNA biopsy needle of the novel type disclosed herein which is typically no larger than 20-22 gauge. The Wang needle is not designed as a fine needle aspiration device but is designed to cut off pieces of lung pleura. A large diameter needle like the Wang device measuring about 4.5 mm in diameter is inappropriate for fine needle biopsy procedures due to the high risk of complications from a large tissue puncture including bleeding, pneumothorax and bile leakage.
The Wang structure includes a notch formed in a first side of the large bore needle and a hole in an opposite side thereof. The tissue to be cut extends into the notch and is sliced off when the outer needle or cannula is advanced as aforesaid. No such opposing hole can be provided in an FNA biopsy needle because such hole would allow the escape of cellular material when it is deposited directly from the syringe barrel onto a microscope slide in which the distal tip bevel and side notch must point in the same direction.
The distal tip of the Wang outer needle is not hollow and therefore no tissue cutting occurs at said distal tip. All tissue cutting occurs at the side of the Wang needle where the notch is positioned. Thus, the Wang needle collects relatively large samples in a knifing action, and performs no scraping action capable of collecting samples at the cellular level.
Neither Wang nor any other known two needle systems include both an open distal end and a port for cutting tissue nor is any core biopsy system capable of collecting samples of cellular thickness. It should also be observed that the Wang needle is attached to a syringe barrel and includes a pressure flap.
Other biopsy tools that collect large specimens include spring-loaded core biopsy guns. An example of a vacuum-assisted biopsy device is the Mammotome Biopsys® breast biopsy device.
The third technique is called fine needle aspiration (FNA) biopsy and is performed with an FNA biopsy needle. An FNA biopsy needle scrapes cells from the tumor or lesion that are so small as to be invisible to the unaided eye. Advantageously, the cellular material is already very thin when it is collected so there is no need to slice it to a thinner size prior to viewing it on a microscope slide because light can already pass through the thin cell layer. The cellular material is deposited onto a microscope slide directly from the FNA biopsy needle, stained, and viewed so that there is less time to the final biopsy report because the slicing machine and all of the handling steps necessitated thereby are eliminated. Trauma to the patient is greatly reduced because of smaller needle diameter and because cells are scraped instead of tissue being cut in thick pieces. Complication risk is also minimized or eliminated due to smaller nozzle diameters.
FNA biopsy needles collect samples by aspiration; a vacuum applied to the proximal end of a hollow needle pulls severed cellular material from the lesion into the lumen of the needle. The needle is then retracted from the soft tissue so that the cellular material in the lumen can be removed for analysis. If more samples of the lesion are needed, the biopsy needle is reintroduced into the lesion.
The primary distinction between an FNA biopsy needle and a core tissue biopsy needle is that the latter cuts or slices relatively large pieces of tissue from a lesion or tumor whereas the former scrapes cellular material from a lesion or tumor. By way of analogy, a core needle aspiration biopsy needle is like a knife that cuts slices of cheese and an FNA biopsy needle is like a cheese grater that scrapes small flakes of cheese.
Sometimes, however, the FNA biopsy procedure fails to collect a sample of sufficient size to enable definitive pathological analysis. When that happens, the physician must repeat the procedure, causing additional trauma to the body part undergoing biopsy and creating an additional risk of an adverse event.
The primary reason that conventional FNA biopsy needles are sometimes unable to collect sufficient cellular material is that the only cutting action occurs at the hollow distal tip of the needle. Thus, no scraping occurs during the retraction stroke of the needle, i.e., scraping occur only in the forward thrust.
Although FNA biopsy needles represent a significant improvement over more invasive procedures for performing biopsies on suspect lesions or tumors, there remains a need for an improved FNA biopsy needle that increases the amount of sample that may be recovered per entrance into the lesion with one needle insertion so that multiple insertions need not be performed to complete a biopsy procedure.
However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the standard FNA biopsy needle could be improved.